Pontoon floatation support



May 27, 1969 T. R. MORTON ET AL 3,446,172

PONTOON FLOATATION SUPPORT Filed Oct. 23; 1967 United States Patent3,446,172 PONTOON FLOATATION SUPPORT Ted R. Morton, Dayton, and GeorgeA. Douglass, Trenton, Ohio, assignors to Armco Steel Corporation,Middletown, Ohio, a corporation of Ohio Continuation-impart ofapplication Ser. No. 533,310, Mar. 10, 1966. This application Oct. 23,1967, Ser. No. 685,992

Int. Cl. B63b 38/00 U.S. Cl. 114-.5 7 Claims ABSTRACT on THE DISCLOSUREA load bearing pontoon floatation support for water floatation systemscomprising a one-piece tube having the same average diameter throughoutits length. The tube is entirely filled with expanded in situ, integral,low density, cellular foam material forming a unitary foamed elementwithin the tube and providing maximum area contact with the interiorsurface of the tube, and means are provided for holding the foamedelement in place within the tube.

CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 533,310, filed Mar. 10,1966, and titled Pontoon Floatation Support, now abandoned.

BACKGROUND OF INVENTION Field of the invention This invention relates tofloatation systems such as, for example, boat docks and piers, and moreparticularly to load bearing pontoon floatation supports which providesupport for such systems in the water.

Description of-the prior art When lake water levels are fixed, docks andthe like may be placed on piling driven into the lake bottom. However,if there is a wide variation in the water level, such docks may besubmerged and nonusable a substantial part of the year, possibly evenbeing carried away. Even if the dock structures are placed upon veryhigh piling to combat the rise of the water, they would be impracticalas they would not accommodate boats most of the year because of theirexcessive height above the waters surface. This necessitates the use ofa floating dock system.

Conventional floating dock systems utilize either drums, welded tanks,pipe or foam billets as floatation supports. Such floatation supportshave proven to be impractical because of the myriad problems anddifliculties associated therewith.

Drums utilized for floatation supports are commonly of the large metaloil drum variety. Such drums have a limited life as supports-probablyabout two years-because they rust and sink. Also the total value of thedrums as floatation is destroyed when they sustain punctures caused bycollision with boats or vandalism such as bullet holes. Naturally, ifthe rusted or punctured drums are secured under a dock framework, theywill become dead weight and appreciably diminish the floatation of thedock. If only partially submerged rusted or punctured drums get free oftheir dock structure, they become very definite safety hazards to waternavigation. In fact, some governmental bodies and specifying agenciesrequire owners of drum supported docks to replace them with permanenttype floatation.

Additionally, the utility of drums in dock construction is limitedbecause of the drum size. Since drums are of ice relatively shortlength, they will not bridge large gaps, thus requiring an endless chainof drums. An endless chain of drums is not very satisfactory because itwill not provide the rigidity needed for a good dock structure.

Foam billet floatation supports are generally constructed of a plasticfoam placed between two wooden plates. The main problem with this typeof floatation support is that it is open and subject to miscellaneousperils. For example, gasoline and oil on the waters surface areparticularly destructive, since they tend to dissolve the foam andeliminate its utility. Naturally, the use of foam billets as afloatation support thereupon vanishes. Additional problems also arisefrom burrowing animals which find the foam a very secure home and frommechanical damage to the foam caused by boats docking, floating ice ordebris.

Additionally, it should be noted that prior art disclosures relating tofloats or buoys have proven to be generally unsatisfactory forload-bearing floatation structures. For example, United States PatentNo. 3,132,417, in the name of H. -B. Irwin, discloses a buoy comprisinga twopiece plastic shell filled with a rigid, molded plastic foam. Eachpiece of the shell is somewhat cup shaped, having an open end. After thefoam material has been provided in each shell half, the halves arejoined together, with their open faces adjacent each other, by means ofan elongated bolt extending through the structure, and a resilient bondor bumper extends peripherally around the structure and engages integralperipheral flanges on the two shell halves.

While Irwin discloses a floatable noncrushable buoy, it is not directedto a load carrying structure. In fact, if a number of the Irwin buoyswere joined together, end to end, to form a floatation support, anonrigid support would result. Further, if the Irwin buoys were made ingreatly elongated form, and adapted for use as a horizontally oriented,load carrying structure, the two-piece construction would render theresulting floatation support very little better than two or more drumsbanded together.

Prior art references relating to water craft disclose numerous pontoons,but these pontoons have proven to be generally most unsatisfactory asload bearing pontoons for floatation support systems. For example,United States Patent No. 2,975,747, in the name of J. Opie, discloses apontoon-type catamarin. The two-piece Opie pontoon comprises acontinuous metal sheet in the form of a U- shaped wall with a metal topcover extending the length of the body of the pontoon and formed fromone or more suitably connected sheets. The top cover has integrallyformed channels along its edges, adapted to receive the top edges of theU-shaped body portion of the pontoon. Opie teaches the filling of thedescribed pontoon with a plurality of flat blocks and pieces ofrelatively light, relatively rigid, nonabsorbent, waterproof material,such as Styrofoam, Unicrest, foam-glass, or equivalent plastic material.Opie also teaches that a one-piece molded plastic material may be usedto fill the interior of the pontoon.

While the Opie pontoon is, perhaps, satisfactory for water craft, it hasproven to be unsatisfactory as a load bearing pontoon for a floatationsupport system because it simply provides a complex and expensivepontoon which, although floatable and uncrushable, does not exhibitenhanced live or static load carrying capabilities.

SUMMARY OF THE INVENTION The present invention provides a load bearingpontoon floatation support for use with dock structures and the like.This support comprises a one-piece tube which has the same averagediameter throughout its length and which is entirely filled withexpanded in situ, integral, low density, cellular foam material forminga unitary foamed element within the tube and providing maximum areacontact within the interior surface of the tube. Additionally, means areprovided for holding the foamed element in place within the tube.

It has been found that when the foam material is pressure expanded insitu within the one-piece tube, to form a unitary foamed elementtherein, and when means are provided for holding the foamed element inplace within the tube, such as depending projections, corrugations,glue, or other adhesives between the inside surface of the tube and thefoamed element, the resulting composite structure demonstratesremarkable and unexpected rigidity. This is of significance because thecomposite structure of the present invention has suflicient strength tospan considerable distances and displays a much larger live or staticload carrying capability than heretofore achievable except by structureswhich were considerably heavier, more complex, and more expensive. Itshould be pointed out that the stiff and rigid pontoon support of thisinvention is able to support much greater live or static loading becausethe combination of the one-piece tube, the foam material expanded insitu, so as to form a unitary foamed element therein providing maximumarea contact with the interior surface of the tube, and means forholding the foamed element in place within the tube, exhibits thesynergistic effect of enhanced shear strength and resisting moment.

The pontoon support of this invention also offers much more utility inthe actual construction of floatation systems because it has the sameaverage diameter throughout its length. This enables use in anyrotatable position about its longitudinal axis.

Additionally, the pontoon support of this invention also provides anincreased transference of force from a point contact on its exterior,i.e., increased bearin strength.

Finally, the maximum area contact of the foamed element with theinterior surface of the one-piece tube and the holding of the foamedelement in place within the tube increases beam stability, and tends topreclude deflection of the pontoon support.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a fragmentary, partialperspective, cut away view of an exemplary pontoon floatation supportaccording to the instant invention.

FIGURE 2 is a perspective view of a conventional oil drum which ispresently much used as a support for floatation systems.

FIGURE 3 is a fragmentary, partial perspective view of a conventionalplastic foam billet which is presently much used as a support forfloatation systems.

FIGURE 4 is a fragmentary, partial perspective cut away view of atypical boat dock floatation system using the pontoon floatationsupports according to the instant invention.

FIGURE 5 is a side elevational view of a water craft using the pontoonfloatation supports according to the mstant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By way of illustration, themeans for holding the foamed element in place within the shell, as willbe more fully explained hereinafter, is described in terms of anexemplary embodiment utilizing corrugations. However, it should beclearly understood that the shell or tube may be smooth walled, as shownin FIGURE 4, and that the means for holding the foamed element in placewithin the shell or tube may comprise depending projections, such asdimples, etc., or glue or other adhesives between the inside surface ofthe shell or tube and the foamed element. Hereinafter, the glue or otheradhesives will be referred to as glue.

Turning now to FIGURE 1, it will be seen that the composite floatationsupport according to the invention comprises a one-piece tube or shell12 having the same average diameter throughout its length and having itsinterior entirely filled with expanded in situ foam material, whichforms a unitary foamed element 14 within the tube 12 providing maximumarea contact with the interior surface of the tube.

It will be understood that by maximum area contact with the interiorsurface of the tube 12 it is meant that the expanded in situ foamedelement 14 contacts the maximum surface area of the interior of the tube12 as is possible when utilizing the hereinafter explained method forpressure expanding the foam material. The maximum area contacted may beless than due to localized shrinkage and the like. It will also beunderstood that when the means for holding the foamed element 14 inplace comprises corrugations, as shown in FIGURE 1, the foamed elementextends into the corrugations. t

The foam material 14 may be characterized as integral,

low density, cellular material having uniform small voids, such as, forexample, polystyrene. Pressure expansion in situ of the polystyrene foammaterial may be accomplished pursuant to the method taught in US. LetterPatent 3,042,967, filed June 18, 1958.

Briefly, the above referred to method comprises the steps: Partiallyinserting steam probes into a molding cavity, blowing partially expandedcellular polystyrene particles capable of further expansion into thecavity so as to substantially fill it, further inserting the probessubstantially all the way into the mold cavity, injecting steam into themold cavity, and after the elapse of a length of curing time,simultaneously stopping the steam injection and removing the probes fromthe mold cavity at a desired rate of removal. Essentially, the describedmethod causes the cellular polystyrene particles to be heated to atemperature wherein they will be softened and expanded so as to take theshape of the mold cavity.

As the best results are realized with the composite floatation support10 of the invention when there is maximum area contact between theexpanded in situ foamed element 14 and the interior surface of the shell12, the aforementioned method should be carefully administered so as toattain the best possible result.

The shell 12 is of uniform cross-section from one end to the other andmay be made of galvanized pipe, as shown in FIGURES 1 and 4, so as to beinexpensive and maintenance free in most applications. Such pipe may, ofcourse, be of the corrugated variety, including helical corrugations asshown in FIGURE 1, if additional rigidity is required. It will beunderstood, however, that other materials, corrugated or uncorrugated,such as plastic, plastic-coated metal, or fiber glass may also beutilized for the tube 12, so long as means are provided to hold thefoamed element providing maximum area contact with the interior surfaceof the shell in place within the tube.

It is important to this invention that the foamed element 14 be held inplace within the tube 12. The means to accomplish this end may comprisecorrugations, which may be helical, as shown in FIGURE 1, or projectionswhich depend from the interior surface of the tube 12, such as dimplesand the like, or glue between the inside surface of the tube 12 and thefoamed element 14. The gluing operation preferably extends over the fulllength of the interior surface of the tube 12. While the holding meansmay comprise corrugations, or depending projections, or glue between theinterior surface of the tube 12 and the foamed element 14, it will beobvious that a combination of the aforementioned elements may beutilized.

The fact that the foamed element 14 is very light and provides maximumarea contact with the interior surface of the tube 12 is of importance,because the composite support 10 is light, buoyant and substantiallynoncrushable.

The cap 16 may be used to close the ends of the composite support 10.This protects the foam element 14 from undercutting by gasoline, oil, orburrowing rodents. Such undercutting 18 is a current problem withconventional foam billets as shown in FIGURE 3.

It should be pointed out that the aforementioned operation of gluingbetween the interior surface of the tube 12 and the foamed element 14 isalso of importance for waterproofing purposes. The glue can, in fact, beutilized primarily as a waterproofing agent, as opposed to beingutilized for both waterproofing and as means to hold the foamed element14 in place within the shell 12, and best waterproofing results arerealized when the glue is utilized for at least one and one-half feet oneach end of the pontoon. However, even when glue is used as awaterproofing agent, the use of end caps 16 is still desirable in orderto protect the ends of the foamed element 14 from undercutting andmechanical damage.

The aforementioned gluing operation, whether for a portion of for theentire length of the pontoon 10, also is of importance in safeguardingagainst localized shrinkage and the like of the foamed element 14 asfoam material is pressure expanded in situ within the shell or tube 12.This is so because the use of glue in this manner improves maximum areacontact between the foamed element 14 and the inside surface of theshell or tube 12.

Inherent in the composite support 10 of FIGURE 1 are the best propertiesof the tube 12 and the polystyrene foamed element 14. The tube 12supplies strength and rigidity, while at the same time is protects thepolystyrene foamed element 14. The polystyrene foamed element 14supplies the necessary floating capabilities and rigidizes the tube 12.Obviously, the composite support 10 may be punctured and still retainits floatation characteristics because the polystyrene foamed element 14assures that it will not sink.

Additionally, it should be noted that a result of the composite pontoonfloatation support according to this invention is that it is a much morepermanent and durable load bearing support than the old-fashioned drums4.0

TABLE I.PONTOON COMPRESSION TESTS USING 4-INCH SQUARE STEEL PAD LOADING6 20 of FIGURE 2, or the foam billets 22 of FIGURE 3.

As was previously explained, an existing problem with conventionalfloatation supports is their inability to span distances. For example, achain of the drums 20 is required to span the smallest of distances.While it is true that a structure so supported will float, it is alsotrue that such a structure will not be the least bit rigid because eachdrum rolls and sways in its own manner. Although the foam billets 22 ofFIGURE 3, composed of the foam 24 in sandwich form between the woodensupports 26, are capable of spanning larger distances than the drums 20,they are not adequate structurally. Also, gasoline, oil and other perilsreadily destroy the foam 24, making it inevitable that it will bereplaced.

The composite floatation support 10 according to this invention isextremely stiff and rigid. Actually, the tube 12 will supply stiffnessor rigidity. However, when the polystyrene foam is pressure expanded insitu within the shell 12 forming a foamed element 14 providing maximumarea contact with the interior surface of the tube, and when means areprovided which hold the foamed element in place within the tube, thecomposite support 10 has much greater rigidity. This rigidity enablesthe composite support 10 to be of utility for structural construction offloatation systems because it can span distances with case (see FIGURE4) and still give the system the rigidity which is required.

It should also be pointed out that the stiff and rigid composite pontoonsupport 10 of this invention is able to support much greater live orstatic loading because the combination of the one-piece tube 12, thefoam material expanded in situ, so as to form a foamed element 14therein which provides maximum area contact with the interior surface ofthe tube 12, and the means for holding the foamed element in place,exhibits the synergistic effect of enhanced shear strength and resistingmoment.

Both compression and beam tests have been performed on the compositepontoon support of this invention, and the following results wereobtained:

Percent increase of pontoons over Def. at Nominal l. ax. same size max.Test No. Specimen diameter, in. Pad location load, lb. shell, percentload, in.

.. Steel shell 18 9 from end 800 7. 0 18 Seam center 9 from end. 4, 380450 4. 9 18 Seam center 11" from end- 1 6, 800 750 2. 7 18 Seam centeron beam 4, 150 420 3. 6

. center.

21 9" from end R 740 6. 4 21 -..-.do 3,400 370 2.3 21 Seam cente end 3,500 380 3. 0 21 ----.do. 715 5. 5 24 J from e 580 5. 5 24 .do 3,850 5701.8 24 Seam center 9" from end. 4, 350 650 3. 0

1 Test was stopped at this point due to the severe deflections of themetal which caused the shell to bear against the machine to such adegree that any further results would have been invalid. Test wasdelayed at 5,700 lbs. to increase load pad height and at 4.990 lb. toswitch load range.

2 Test stopped when shell deflected to bear against test machine. Whenshell was repos1t1oned and reloaded, max. load was 520 lb. at adeflection of 4.4 in.

TABLE II.PONTOON BEAM TESTS USING 4INCH SQUARE STEEL PADS AT THE HOODAND REACTION POINTS Percent Size increase of pontoons over Third pointNorn Length, Max. same size deflection at Test No. Specimen I.D., inSpan, ft. load, b. shell, percent max. load, in.

1 Steel shell 18 12 11 2, 300 3 7. 0 2..- Pontoon. 18 12 ll 3, 850 67 5.6 5 Steel shell. 21 12 11 2, 500 10. 2+ 6-.. Pontoon- 21 12 11 4, 900 965. 8 7 .410 21 12 11 5, 200 108 4. 2 3 Steel shell 24 12 11 2,050 4.-.Pontoon. 24 12 11 5, 900 188 5. 8 6 -.do. 24 12 11 6, 300 207 4. 9

l Polystyrene filler glued along entire pipe length.

2 Head deflected 11 in., its maximum, where load was removed andcrosshead lowered before reloadlng and deflecting 7.5 in. when test washalted due to buckling beyond capacity of machine.

Typical failure in unfilled pontoon specimens was by buckling and infilled pontoon specimens by seam splitting.

3 Third point deflection was 7.0 in. when deflection transducer was atend of the range and recorder had to be turned off. Estimated deflectionat max. load was 7.5 in.

The tests of Tables I and II disclose the superiority of the pontoonfloatation supports of this invention, along with the fact that theexpanded in situ foam material adds considerable strength to the shellby primarily confining deformation to local distortion at load points.

The series of compression tests of Table I were performed with the loadapplied through 4 inch square steel pads located 9 inches from thepontoon end. The pontoons tested had the foamed element glued to theinside surface of the steel shell for approximately 1% feet from bothends. Many of these specimens failed by a split seam on top of the steelshell at the edge of the load pads. In order to minimize this type offailure, the remaining specimens were positioned with a seam centeredunder the load pads.

It should be noted that test number 8 of Table I was performed on thecenter of the 18 inch pontoon where the foamed element was not glued tothe inside surface of the shell, and a 5.3% lower load than the standard9 inch test was obtained.

The results of the compression tests demonstrate that the foam material,expanded in situ Within the shell so as to form a foamed elementproviding maximum area contact with the interior surface of the shell,and the means (corrugations) for holding the foamed element in placewithin the shell, are beneficial under concentrated loading (average of510% increase with the foam material). This is considered significantbecause in actual use the pontoon loads are transferred by concentratedloading similar to the test conditions.

The series of concentrated beam tests of Table II were performed using 4inch square steel pads at the load and reaction points. The pontoonstested, except for tests 6 and 7, had the foamed element glued to theinside surface of the steel shell for approximately 1% feet from bothends. Typical failure of a tested pontoon occurred by buckling at theload points, or by a heart-shaped buckling at the ends at the reactionpoints.

As seen in Table II, the foamed element and the corrugations which holdthe foamed element in place within the shell increased the maximum loadan average of 133%. It should also be noted that as the diameter of thepontoon increased the foamed element became significantly moreimportant. Tests 6 and 7 were especially prepared specimens to test theimportance of both the foamed elements being glued to the inside surfaceof the shell for the entire length of the pontoon and the use ofcorrugations. As can be seen, the pontoons of tests 6 and 7 withstoodapproximately 6% more load than the other pontoons which only utilizedglue for 1% feet at each end.

A typical floatation system utilizing composite floatation supports 10(smooth walled shell with gluing and/ or depending projections)according to the instant invention is shown in FIGURE 4. It will be seenthat the composite supports 10 have been topped with the deck 28. Thedeck 28 may, of course, be of any suitable material and construction,the only general restriction being that it should preferably beperforated to permit surface water drainage. It has been found that thepreferable decking is a galvanized steel interlock grating. Thiseliminates the disadvantages of wooden decks: thousands of splinters,the danger of burning, the tendency to rot out after a few seasons ofuse, nail protrusion, and warping and swelling. The main deck 34 runsthe length of the entire structure and the side decks 36, substantiallynormal to the main deck 34, make up the individual boat portals 38. Ofcourse, roofed dock structures which utilize the pontoon floatationsupports of the instant invenion also may be constrt tcd,

The typical floatation system of FIGURE 4 generally will utilize pontoonfloatation supports, the shells 12 of which are of cylindrical ZO-gaugegalvanized pipe of a 24 inch diameter. The length to diameter ratio ofsuch a support will normally be 4 to l or greater. It should be noted,however, that, depending on the specific application, the diameter ofthe shell 12 may vary from 12 inches to 36 inches or greater and be of.0375 to .25 inch wall thickness.

It will thus be apparent that tee docks, head docks and finger docks, inall sizes and shapes may be built with easily assembled floatationsupports according to the present invention.

Additionally, the pontoon .floatation support 10 may be used in watercraft, as shown in FIGURE 5. Essentially, the pontoon floatationsupports 10 are fitted at their ends with the partial cone heads 42. Thestruts 44 are mounted on top of the pontoon supports 10 and hold theplatform 46. A deck railing 8 along with power means completes the watercraft.

It will thus be seen that the myriad of uses for a floatation support 10according to the instant invention are limited only by imagination.

What we claim is:

1. A load bearing pontoon floatation support for water floatationsystems comprising a one-piece tube capable of withstanding shockwithout rupture and permanent deformation, said t-ube having the sameaverage diameter throughout its length and being entirely filled withexpanded in situ integral, low density cellular foam material forming aunitary foamed element within said tube and providing maximum areacontact with the interior surface of said tube, and means for holdingsaid foamed element in place Within said tube, said holding meanscomprising circumferential corrugations in said tube extendingsubstantially the length thereof, each said corrugation providing abreak in the interior surface of said tube, and wherein said foamedelement extends into said corrugations.

2. The pontoon floatation support according to claim 1, including endcaps secured to and closing the ends of said tube.

3. The pontoon floatation support according to claim 1, wherein saidcorrugations are helical.

4. The pontoon floatation support according to claim 1, wherein saidholding means includes adhesive material between the inside surface ofsaid tube and said foamed element.

5. The pontoon floatation support according to claim 4, wherein saidadhesive material is provided for the full length of said tube.

6. The pontoon floatation support according to claim 4, including endcaps secured to and closing the ends of said tube.

7. The pontoon floatation support according to claim 3, including endcaps secured to and closing the ends of said tube.

References Cited UNITED STATES PATENTS 3,063,398 11/1962 Yohe 11466.53,132,417 5/1964 Irwin 9-8 X 3,340,553 9/1967 Jones 114-.5 X

TRYGVE M. BLIX, Primary Examiner.

US. Cl. X.R. 11461

